The present invention relates to a pneumatic tire and more particularly an improvement in a tread reinforcing belt.
In general, a pneumatic tire is provided radially outside the carcass with a belt to reinforce the tread portion.
In a conventional belt structure, as shown in FIGS. 7 and 8, a belt ply (p) is formed by applying a strip (e) of rubberized parallel cords (b) around the carcass. A strip (e) of rubberized parallel cords (b) is made by cutting a sheet of tire fabric (d) at a bias angle (.alpha.). The ends (f) of the applied strip (e) are jointed by overlapping one upon the other by a certain width, and a joint running at the bias angle (.alpha.) is formed, and further two side edges with cord cut ends are formed. Therefore, due to the bias joint, steering stability and directional stability during straight running are liable to be disturbed. It is especially remarkable during high speed running. Further, durability is impaired due to the cord cut ends from which rubber separation failure arises.
In order to solve those problems, a jointless belt formed by spirally winding a continuous cord around the carcass at a small angle to the tire equator has been proposed in, for example, Japanese Utility-Model Publication No. 58-160805. However, due to the spiral cord arrangement, drifting toward a certain direction is liable to occur.